Double mass flywheel

ABSTRACT

A double mass flywheel has an inertia member, a flexible plate, a second flywheel, an elastic member, and a friction generation mechanism. The flexible plate is deformable in a bending direction and connects the inertia member to a crankshaft. The second flywheel is formed with a clutch friction surface. The elastic member elastically connects the second flywheel to the crankshaft in the rotational direction. The friction generation mechanism is located functionally in parallel with the elastic member in the rotational direction. The friction generation mechanism is held by the flexible plate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a double mass flywheel. More specifically, the present invention relates to a double mass flywheel having a first flywheel fixed to a crankshaft and a second flywheel connected to a crankshaft through elastic members.

2. Background Information

Conventionally, a flywheel is attached to a crankshaft of an engine for absorbing vibrations caused by variations in engine combustion. Further, a clutch device is usually arranged on a transmission side (i.e., in a position axially shifted toward the transmission) with respect to a flywheel. The clutch device usually includes a clutch disk assembly coupled to an input shaft of the transmission, and a clutch cover assembly for biasing the frictional coupling portion of the clutch disk assembly toward the flywheel. The clutch disk assembly typically has a damper mechanism for absorbing and damping torsional vibrations. The damper mechanism has elastic members such as coil springs arranged to compress in a rotating direction.

A structure is also known in which the damper mechanism is not arranged in the clutch disk assembly, and rather is arranged between the flywheel and the crankshaft. In this structure, the flywheel is located on the output side of a vibrating system, in which the coil springs form a border between the output and input sides, so that inertia on the output side is larger than that in other prior art. Consequently, the resonance rotation speed can be lower than an idling rotation speed so that damping performance is improved. The structure, in which the flywheel and the damper mechanism are combined as described above, provides a flywheel assembly or a flywheel damper, an example of which is disclosed in Japanese Unexamined Publication H04-231757, which is hereby incorporated by reference. The flywheel fixed to the crankshaft of the engine is called a first flywheel, and the flywheel connected to the crankshaft via the elastic members is called a second flywheel.

The friction generation mechanism is located to operate in parallel with the elastic members of the damper mechanism in the rotational direction. When the second flywheel rotates relative to the crankshaft, the elastic members of the damper mechanism are compressed in the rotational direction and the friction generation mechanism generates frictional resistance. As a result, torsional vibrations due to the combustion fluctuations of the engine are quickly dampened.

The friction generation mechanism may have a friction generation portion and a rotational engagement portion functionally located in series with the friction generation portion in the rotational direction. The rotational engagement portion is made of two members defining a minute rotational gap between them. Accordingly, when the minute torsional vibrations occur due to the combustion fluctuations of the engine, the two members do not abut each other in the rotational engagement portion so as not to operate the friction generation mechanism. As a result, the torsional vibrations are effectively absorbed or dampened.

The friction generation mechanism is likely to be affected by heat from the clutch friction surface of the second flywheel. If the friction generation mechanism is held by the second flywheel side member, the fiction performance is not stable. For example, the friction coefficient is changed due to the exposure of the friction generating mechanism to heat.

In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved double mass flywheel. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.

SUMMARY OF THE INVENTION

It is an object of the present invention to stabilize the performance of a friction generation mechanism in a double mass flywheel.

According to a first aspect of the present invention, a double mass flywheel is provided to receive torque from a crankshaft of an engine. The double mass flywheel includes a first flywheel, a second flywheel, an elastic member, and a friction generation mechanism. The first flywheel is fixed to the crankshaft. The second flywheel is formed with a clutch friction surface. The elastic member elastically and directly connects the second flywheel to the crankshaft in the rotational direction. The friction generation mechanism is located functionally in parallel with the elastic member in the rotational direction. The friction generation mechanism is held by the first flywheel.

In this double mass flywheel, when the second flywheel rotates relative to the crankshaft due to torsional vibrations, the elastic member is compressed in the rotational direction and the friction generation mechanism operates to generate friction. Accordingly, torsional vibrations are quickly dampened. The friction generation mechanism is unlikely to be affected by heat from the clutch friction surface of the second flywheel because the friction generation mechanism is held by the first flywheel. As a result, the performance of the friction generation mechanism is stable. Especially since heat from the second flywheel is unlikely to be transmitted to the first flywheel because the first flywheel is not connected to the second flywheel through the elastic member, the performance of the friction generation mechanism is stable.

A double mass flywheel in accordance with a second aspect of the present invention is the double mass flywheel of the first aspect, wherein the first flywheel includes a plate member having a radially inner end fixed to the crankshaft, and an inertia member fixed to a radially outer end of the plate member.

A double mass flywheel in accordance with a third aspect of the present invention is the double mass flywheel of the second aspect, wherein the friction generation mechanism is held by a radially outer portion of the plate member.

A double mass flywheel in accordance with the fourth aspect of the present invention is the double mass flywheel of the third aspect, wherein the first flywheel further includes a second plate member fixed to a radially outer portion of the plate member to define an axial space with the plate member. The friction generation mechanism is disposed within the space.

A double mass flywheel in accordance with a fifth aspect of the present invention is the double mass flywheel of second or third aspect, wherein the friction generation mechanism utilizes a part of the inertia member as a friction surface. Accordingly, the number of components is small and the whole structure is simplified relative to conventional structures.

A double mass flywheel in accordance with a sixth aspect of the present invention is the double mass flywheel of the fifth aspect, wherein the friction generation mechanism is located within a space between an axial engine-side surface of the inertia member and an axial transmission-side surface of the plate member. The friction generation mechanism includes a friction member contacting the axial engine-side surface of the inertia member, a plate engaged with the plate member to move in the axial direction but not to rotate relatively, and an urging member located between the axial transmission-side surface of the plate member and the plate to urge elastically the plate toward the friction member. Abnormal sound is unlikely to diffuse into the plate member when the friction generation mechanism operates because the friction member is not in contact with the plate member.

A double mass flywheel in accordance with a seventh aspect of the present invention is the double mass flywheel of any of the second to sixth aspects, wherein the plate member is a flexible plate deformable in a bending direction substantially parallel to an axis of rotation of the crankshaft.

A double mass flywheel in accordance with an eighth aspect of the present invention is the double mass flywheel of any of the first to seventh aspects, wherein the friction generation mechanism is located radially outward of the clutch friction surface. The friction generation mechanism is unlikely to be affected by the heat from the clutch friction surface because the friction generation mechanism is separated from the clutch friction surface in the radial direction.

According to a ninth aspect of the present invention a double mass flywheel is provided to receive a torque from a crankshaft of an engine. The double mass flywheel includes an inertia member, a flexible plate, a second flywheel, an elastic member, and a friction generation mechanism. The flexible plate is deformable in a bending direction of the crankshaft and connects the inertia member to the crankshaft. The second flywheel is formed with a clutch friction surface. The elastic member elastically connects the second flywheel to the crankshaft in the rotational direction. The friction generation mechanism is located to operate functionally in parallel with the elastic member in the rotational direction. The friction generation mechanism is held by the flexible plate.

In this double mass flywheel, when the second flywheel rotates relative to the crankshaft due to combustion fluctuations of the engine, the elastic member is compressed in the rotational direction and the friction generation mechanism operates to generate friction. Accordingly, torsional vibrations are quickly dampened. The friction generation mechanism is unlikely to be affected by heat from the clutch friction surface of the second flywheel because the friction generation mechanism is held by the flexible plate. As a result, the performance of the friction generation mechanism is stable.

A double mass flywheel in accordance with a tenth aspect of the present invention is the double mass flywheel of the ninth aspect, wherein the friction generation mechanism utilizes a part of the flexible plate as a friction surface. Accordingly, the number of components is small and the whole structure is simplified.

A double mass flywheel in accordance with an eleventh aspect of the present invention is the double mass flywheel of the ninth aspect, wherein the friction generation mechanism utilizes a part of the inertia member as a friction surface. Accordingly, the number of components is small and the whole structure is simplified.

A double mass flywheel in accordance with a twelfth aspect of the present invention is the double mass flywheel of the eleventh aspect, wherein the frictional resistance mechanism is located within a space between an axial engine-side surface of the inertia member and an axial transmission-side surface of the flexible plate. The friction generation mechanism includes a friction member contacting the axial engine-side surface of the inertia member, a plate engaged with the flexible plate to move in the axial direction but not to rotate relatively, and an urging member located between the axial transmission-side surface of the flexible plate and the plate to urge elastically the plate toward the friction member. Abnormal sounds are unlikely to diffuse into the flexible plate when the friction generation mechanism operates because the friction member is not in contact with the flexible plate.

A double mass flywheel in accordance with a thirteenth aspect of the present invention is the double mass flywheel of any of the ninth to twelfth aspects, wherein the friction generation mechanism is located radially outward of the clutch friction surface. The friction generation mechanism is unlikely to be affected by the heat from the clutch friction surface because the friction generation mechanism is separated from the clutch friction surface in the radial direction.

A double mass flywheel in accordance with a fourteenth aspect of the present invention is the double mass flywheel of any of the ninth to the thirteenth aspects, and further a fixing member to fix the inertia member to the flexible plate. The friction generation mechanism is located adjacent to a radially inner side of the fixing member.

These and other objects, features, aspects, and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of this original disclosure:

FIG. 1 is a schematic cross-sectional view of a double mass flywheel in accordance with a first preferred embodiment of the present invention;

FIG. 2 is an alternate schematic cross-sectional view of the double mass flywheel;

FIG. 3 is an elevational view of a flywheel assembly of the double mass flywheel with sections removed for illustrative purposes;

FIG. 4 is an enlarged fragmentary cross-sectional view that particularly illustrates a second friction resistance generating mechanism of the double mass flywheel;

FIG. 5 is an elevational view of the second friction generation mechanism;

FIG. 6 is an enlarged elevational view of the second friction generation mechanism in FIG. 5 with sections removed for illustrative purposes;

FIG. 7 is an enlarged cross-sectional view of a first friction generation mechanism of the double mass flywheel;

FIG. 8 is an alternate enlarged cross-sectional view of the first friction generation mechanism;

FIG. 9 is an enlarged elevational view of the first friction generation mechanism;

FIG. 10 is an elevational view of a first friction washer of the first friction generation mechanism;

FIG. 11 is an elevational view of an input disk-like plate of a damper mechanism of the double mass flywheel;

FIG. 12 is an elevational view of a washer of the first friction generation mechanism;

FIG. 13 is an elevational view of a cone spring of the first friction generation mechanism;

FIG. 14 is an elevational view of a second friction washer of the first friction generation mechanism;

FIG. 15 is a view of a mechanical circuit diagram of a damper mechanism and the friction generation mechanisms of the double mass flywheel;

FIG. 16 is a diagram of torsional characteristics of the damper mechanism and the friction generation mechanisms;

FIG. 17 is a diagram of torsional characteristics of the damper mechanism and the friction generation mechanisms;

FIG. 18 is a diagram of torsional characteristics of the damper mechanism and the friction generation mechanisms;

FIG. 19 is a diagram of torsional characteristics of the damper mechanism and the friction generation mechanisms;.

FIG. 20 is a schematic cross-sectional view of a dual-mass flywheel in accordance with a second preferred embodiment of the present invention; and

FIG. 21 is an alternate schematic cross-sectional view of the dual-mass flywheel of FIG. 20.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Selected embodiments of the present invention will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments of the present invention are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

1. First Embodiment

(1) Structure

1) Overall structure

As seen in FIGS. 1 and 2, a double mass flywheel or flywheel damper 1 in accordance with a first preferred embodiment of the present invention is provided to transmit torque from a crankshaft 91 on an engine side to an input shaft 92 on an transmission side by way of a clutch including a clutch disk assembly 93 and a clutch cover assembly 94. The double mass flywheel 1 has a damper function to absorb and to attenuate torsional vibrations. The double mass flywheel 1 is mainly made of a first flywheel 2, a second flywheel 3, a damper mechanism 4, a first friction generation mechanism 5, and a second friction generation mechanism 6.

In FIGS. 1 and 2, O-O indicates a rotation axis of the double mass flywheel 1 and the clutch. An engine (not shown) is disposed on the left side in FIGS. 1 and 2, and a transmission (not shown) is disposed on the right side. In the following description, the left side in FIGS. 1 and 2 will be referred to as the engine side, which is based on the axial direction, and the right side will be referred to the transmission side, which is also based on the axial direction. In FIG. 3, an arrow R1 indicates a drive side, i.e., forward side in the rotational direction, and an arrow R2 indicates a reverse drive side (rearward side in the rotational direction). The numerical values in the following embodiments are shown as examples and do not limit the present invention.

2) First Flywheel

The first flywheel 2 is fixed to the tip of the crankshaft 91. The first flywheel 2 ensures a large moment of inertia on the crankshaft side. The first flywheel 2 principally includes a flexible plate 11 and an inertia member 13.

The flexible plate 11 is provided to absorb bending vibrations from the crankshaft 91 as well as to transmit torque from the crankshaft 91 to the inertia member 13. Accordingly, the flexible plate 11 has a high rigidity in the rotational direction but a relatively low rigidity in the axial and bending directions. Specifically, the axial rigidity of the flexible plate 11 is equal to or below 3000 kg/mm, preferably in the range between 600 kg/mm and 2200 kg/mm. The flexible plate 11 is a disk-like plate having a central hole and preferably made of a metal plate, for example. The radially inner end of the flexible plate 11 is fixed to the tip of the crankshaft 91 by a plurality of bolts 22. Bolt through-holes are formed in the flexible plate 11 in positions corresponding to the bolts 22. The bolts 22 are mounted on the crankshaft 91 from the axial-direction transmission side.

The inertia member 13 has a thick block shape when viewed cross-sectionally, and is fixed to the axial-direction transmission side on the radially outer edge of the flexible plate 11. The radially outer portion of the flexible plate 11 is fixed to the inertia member 13 by a plurality of circumferentially aligned rivets 15. A ring gear 14 that is provided to facilitate engine startup is fixed to the outer circumferential surface of the inertia member 13. The first flywheel 2 may also be constructed as an integral member.

3) Second Flywheel

The second flywheel 3 is an annular disk-like member, and is disposed on the axial-direction transmission side of the first flywheel 2. The second flywheel 3 has a friction surface 3 a formed on the axial-direction transmission side. The friction surface 3 a is an annular, flat surface. Further, the friction surface 3 a is a portion that engages a clutch disk assembly 93 described hereinafter. The second flywheel 3 has an inner cylindrical portion 3 b extending toward the engine in the axial direction from the inner circumferential edge of the second flywheel 3. A radially inner portion of the second flywheel 3 is formed with a plurality of through holes 3 d aligned in the circumferential direction with the bolts 22, such that the bolts 22 can pass therethrough.

4) Damper Mechanism

The damper mechanism 4 is described below. The damper mechanism 4 elastically engages the second flywheel 3 and the crankshaft 91 in the rotational direction. Therefore, the second flywheel 3 with the damper mechanism 4 constitutes a flywheel assembly or a flywheel damper because the second flywheel 3 is connected to the crankshaft 91 by way of the damper mechanism 4. As shown in FIGS. 1, 2, and 3, the damper mechanism 4 is composed of a plurality of coil springs (elastic members) 34, 35, and 36, a pair of output disk-like plates (output member) 32 and 33, and an input disk-like plate (input member) 20. As shown in the mechanical circuit of FIG. 15, the coil springs 34, 35, and 36 are located to operate functionally in parallel with the first and second friction generation mechanism 5 and 6 in the rotational direction.

Referring now to FIGS. 1, 2, and 3, the pair of output disk-like plates 32 and 33 is composed of a first plate 32 on the axial-direction engine side, and a second plate 33 on the axial-direction transmission side. Both plates 32 and 33 are disk-like members, and are disposed with a certain distance therebetween in the axial direction. A plurality of window portions 46 and 47 aligned in the circumferential direction are respectively formed in each of the plates 32 and 33. The window portions 46 and 47 are structures that support the coil springs 34 and 35 (described hereinafter) in the axial and rotational directions, hold the coil springs 34 and 35 in the axial direction, and have upwardly cut portions that make contact at both ends in the circumferential direction thereof. As seen in FIG. 3, the number of the window portions 46 and 47 is preferably and respectively two, for a total of four. The window portions 46 and 47 are aligned alternately in the circumferential direction in the same radial position. Furthermore, the plates 32 and 33 are formed with a plurality of third window portions 48 aligned in the circumferential direction. The number of the third window portions 48 is preferably two. The third window portions 48 are opposed to each other in a radial direction. Specifically, the third window portions 48 are formed radially outward of the first window portions 46 and support the third coil springs 36 described hereinafter in the axial and rotational direction.

As seen in FIGS. 1 and 2, the first plate 32 and the second plate 33 maintain a distance in the axial direction at the radially inner portions, but are in contact with each other at the radially outer portions and fixed to each other by rivets 41 and 42. As seen in FIG. 3, the first rivets 41 are aligned in the circumferential direction. As seen in FIG. 2, the second rivets 42 are respectively disposed at cut and raised contact portions 43 and 44 of the first plate 32 and the second plate 33. As shown in FIGS. 2 and 3, the contact portions 43 and 44 are formed in two positions diametrically opposing each other. Specifically, the contact portions 43 and 44 are formed radially outward of the second window portion 47. The axial position of the contact portions 43 and 44 is the same as that of the input disk-like plate 20. Further, the second plate 33 is fixed to the second flywheel 3 through rivets 49 at each of the radially outer portions.

Referring now to FIGS. 1, 2, and 11, the input disk-like plate 20 is a disk-like member disposed between the plates 32 and 33. The input disk-like plate 20 has a plurality of first window holes 38 corresponding to the window portions 46, and second window holes 39 corresponding to the first window portions 47. As seen in FIGS. 3 and 11, the first and second window holes 38 and 39 have a straight or slightly curved radially inner edge having a recess 38 a and 39 a extending radially inward at the circumferentially middle portion. The input disk-like plate 20 is formed with a central hole 20 a and a plurality of through holes 20 b for bolts to be inserted around the central hole 20 a. The input disk-like plate 20 has a plurality of protrusions 20 c extending radially outward from the radially outer edge at the locations circumferentially between the window holes 38 and 39. The protrusions 20 c are positioned circumferentially apart from the contact portions 43 and 44 of the output disk-like plates 32 and 33 and the third coil springs 36 such that the protrusion 20 c can collide with either of them in the circumferential direction. In other words, the protrusions 20 c and the contact portions 43 and 44 constitute a stopper mechanism 71 of the damper mechanism 4. Furthermore, spaces between the protrusions 20 c in the circumferential direction function as third window holes 40 to accommodate the third coil springs 36. Referring to FIGS. 9 and 11, in addition, the input disk-like plate 20 is formed with a plurality of holes 20 d. The number of holes 20 d is preferably four. Each hole 20 d has a circular portion at its radial outermost section. The rotational positions of the holes 20 d are between the window holes 38 and 39 in the circumferential direction, and the radial position of the holes 20 d are the same as or close to those of the recesses 38 a

Referring again to FIGS. 1 and 2, the input disk-like plate 20 is fixed to the crankshaft 91 together with the flexible plate 11, a reinforcement member 18, and a support member 19. The radially inner portion of the flexible plate 11 is in contact with an axially transmission side surface of a tip surface 91 a of the crankshaft 91. The reinforcement member 18 is a disk-like member and is in contact with an axially transmission side surface of the radially inner portion of the flexible plate 11.

The support member 19 is composed of a disk-like portion 19 b and a cylindrical portion 19 a that extends to the axial-direction transmission side from the radially outer edge. The disk-like portion 19 b is in contact with an axially transmission side surface of the reinforcement member 18. The disk-like portion 19 b is formed with through holes for the bolts 22 and is fixed to the crankshaft 91. The disk-like portion 19 b is an annular flat portion and the cylindrical portion 19 a extends toward the transmission in the axial direction from a radially inner edge. The inner circumferential surface of the cylindrical portion 19 a is in contact with the outer circumferential surface of a cylindrical projection 91 b formed at the center of the tip of the crankshaft 91 so that the support member 19 is centered in the radial direction. The inner circumferential surface of the input disk-like plate 20 is in contact with the outer circumferential surface of a cylindrical portion 19 a at an axially transmission side portion so that the input disk-like plate 20 is centered in the radial direction. A bearing 23 is attached to the inner circumferential surface of the cylindrical portion 19 a to support the tip of the input shaft 92 of the transmission. In addition, the members 11, 18, 19, and 20 are fastened to each other by screws 21.

As described above, the support member 19 is fixed to the crankshaft 91 such that the support member 19 is centered relative to the crankshaft 91. Further, the support member 19 centers the first flywheel 2 and the second flywheel 3 in the radial direction. That is, the one member has a plurality of functions so that the number of the components is reduced along with manufacturing costs.

The inner circumferential surface of the cylindrical portion 3 b of the second flywheel 3 is supported by an outer circumferential surface of the cylindrical portion 19 a of the support member 19 through a bush 30. As described above, the second flywheel 3 is supported and centered by the support member 19 relative to the first flywheel 2 and the crankshaft 91. The bush 30 further has a radial bearing portion 30 a already described and a thrust bearing portion 30 b disposed between the radially inner portion of the input disk-like plate 20 and a tip of the cylindrical portion 3 b of the second flywheel 3. As a result, a thrust load from the second flywheel 3 is received by the members 11, 18, 19, and 20, which are aligned in the axial direction through the thrust bearing portion 30 b. In other words, the thrust bearing portion 30 b of the bush 30 functions as a thrust bearing supported by the radially inner portion of the input disk-like plate 20 for an axial load from the second flywheel 3. The load generated at the thrust bearing portion 30 b is stable because the radially inner portion of the input disk-like plate 20 is flat and the flatness is improved. Furthermore, the length of the thrust bearing portion 30 b is long enough to stabilize hysteresis torque because the radially inner portion of the input disk-like plate 20 is flat. Furthermore, the radially inner portion of the input disk-like plate 20 is unlikely to be deformed since it is in direct contact with the disk-like portion 19 b of the support member 19 such that there is no space in the axial direction.

The first coil spring 34 is disposed in the first window holes 38 and the first window portions 46. Rotational ends of the first coil spring 34 are in contact with or close to rotational end surfaces of the first window holes 38 and the first window portion 46.

As shown in FIG. 3, the second coil springs 35 are disposed in the second window holes 39 and the second window portions 47. The second coil spring 35 is made of a large and a small spring. Thus, the second coil spring 35 has a higher rigidity than the first coil spring 34. Rotational ends of the second coil spring 35 are in contact with or close to rotational end surfaces of the second window portion 47 but are separated in the circumferential direction from rotational end surfaces of the second window hole 39 by a certain angle, which is preferably four degrees in this embodiment. Referring now to FIGS. 1 and 3, the first coil springs 34 and the second coil springs 35 are aligned in the circumferential direction, wherein the radial positions are the same. The first coil springs 34 and the second coil springs 35 are disposed radially inward of a portion of the clutch friction surface 3 a against which the friction facing 93 a is pressed, i. e., the springs 34 and 35 do not have any portion which is positioned radially outward of the inner circumferential edge of the clutch engagement portion. Accordingly, the axial dimension of the flywheel assembly is reduced because the first and second coil springs 34 and 35 are located radially inward of the clutch friction surface 3 a of the second flywheel 3.

The third coil springs 36 are disposed in the third window holes 40 and the third window portions 48. The third coil springs 36 are smaller than the second and third coil springs 34 and 35. Further, the rigidity of the third coil springs 36 is higher than that of the first and second coil springs 34 and 35, and preferably at least twice as rigid.

5) Friction Generation Mechanism

5-1) First Friction Generation Mechanism

The first friction generation mechanism 5 operates between the input disk-like plate 20 and the output disk-like plate 32 and 33 of the damper mechanism 4 in parallel with the coil springs 34, 35, and 36 in the rotational direction. The first friction generation mechanism 5 generates a certain frictional resistance (hysteresis torque) when the second flywheel 3 rotates relative to the crankshaft 91. The first generation mechanism 5 generates friction over the entire torsional angle region and is not excessively high.

The first friction generation mechanism 5 is disposed radially inward of the damper mechanism 4 and axially between the first plate 32 and the second flywheel 3. As seen in FIGS. 1, 7, and 8, the first friction generation mechanism 5 is composed of a first friction member 51, a second friction member 52, a cone spring (urging member) 53, and a washer 54.

The first friction member 51 rotates together with the input disk-like plate 20 to slide against the first plate 32 in the rotational direction. As shown in FIGS. 7-10, the first friction member 51 has an annular portion 51 a, and first and second engagement portions 51 b and 51 c extending from the annular portion 51 a. The annular portion 51 a contacts the radially inner portion of the first plate 32 to slide in the rotational direction. The first engagement portions 51 b and the second engagement portions 51 c are located alternately in the circumferential direction. The first engagement portion 51 b has a shape extending in the circumferential direction with a narrow width in the radial direction. In other words, the first engagement portion 51 b is slot-shaped. The first engagement portion 51 b is engaged with the recesses 38 a and 39 a of the window holes 38 and 39 of the input disk-like plate 20. The second engagement portion 51 c has a shape extending in the rotational direction but not to the extent of the first engagement portion 51 b. The second engagement portion 51 c is engaged with the hole 20 d of the input disk-like plate 20. Accordingly, the first friction member 51 can move relative to the input disk-like plate 20 in the axial direction, but not in the rotational direction.

A first protrusion 51 d is formed at the circumferentially middle position of the tip of the first engagement portion 51 b and extends in the axial direction from the first engagement portion 51 b. A pair of first axial end surfaces 51 e is formed on the circumferential sides of the first protrusion 51 d. Furthermore, a second protrusion 5 f is formed at the radially inward portion of the tip of the second engagement portion 51 c. A first axial end surface 51 g is formed radially outward of the second protrusion 51 f.

The second friction member 52 rotates together with the input disk-like plate 20 to slide against the second flywheel 3 in the rotational direction. As shown in FIGS. 7, 8, 9, and 14, the second friction member 52 is an annular member and contacts a second friction surface 3 c, which is in the radially inner portion of the second flywheel 3. The second friction surface 3 c is a concave portion that extends toward the transmission in the axial direction further than any other portion of the first friction generating mechanism 5 on the engine side of the second flywheel 3, and is an annular flat surface.

The second friction member 52 is formed with a plurality of recesses 52 a aligned in the circumferential direction at the inner circumferential edge. The first protrusion 51 d of the first engagement portion 51 b and the second protrusion 51 f of the second engagement portion 51 c are respectively engaged with the recesses 52 a. Accordingly, the second friction member 52 can move relative to the first friction member 51 in the axial direction, but not in the rotational direction.

The cone spring 53 is disposed axially between the first friction member 51 and the second friction member 52 and urges each of the members in axially opposite directions. As shown in FIG. 13, the cone spring 53 is a conical or disk-like member formed with a plurality of recesses 53 a at the inner circumferential edge. Referring now to FIGS. 7 to 10, the first protrusion 51 d of the first engagement portion 51 b and the second protrusion 51 f of the second engagement portion 51 c are respectively engaged with the recesses 53 a. Accordingly, the cone spring 53 can move relative to the first friction member 51 in the axial direction, but not in the rotational direction.

The washer 54 is provided to ensure or to stabilize the transfer of a load of the cone spring 53 to the first friction member 51. As shown in FIG. 12, the washer 54 is an annular member and is formed with a plurality of recesses 54 a aligned in the circumferential direction at the radially inner edge. Referring now to FIGS. 7, 8, and 9, the first protrusion 51 d of the first engagement portion 51 b and the second protrusion 51 f of the second engagement portion 51 c are respectively engaged with the recesses 54 a. Accordingly, the washer 54 can move relative to the first friction member 51 in the axial direction, but not in the rotational direction. Referring now to FIGS. 7 and 8, the washer 54 is received on the first axial end surface 51 e of the first engagement portion 51 b and the second axial end surface 51 g of the second engagement portion 51 c. The radially inner portion of the cone spring 53 is supported by the washer 54 and the radially outer portion of the cone spring 53 is supported by the second friction member 52.

5-2) Second Friction Generation Mechanism

Referring now to FIGS. 1, 2, 4, and 5, the second friction generation mechanism 6 operates between the input disk-like plate 20 and the output disk-like plate 32 and 33 of the damper mechanism 4 in parallel with the coil springs 34, 35, and 36. The second friction generation mechanism 6 generates a relatively large frictional resistance (hysteresis torque) over the whole range of the torsional characteristics when the second flywheel 3 rotates relative to the crankshaft 91. In this embodiment, the hysteresis torque generated by the second friction generation mechanism 6 is preferably from five to ten times that generated by the first friction generation mechanism 5.

The second friction generation mechanism 6 is made of a plurality of washers contacting with each other disposed in an axial space between an annular portion 11 a at the radially outer portion of the flexible plate 11 and a second disk-like plate 12 disposed axially between the flexible plate 11 and the inertia member 13. The washers of the second friction generation mechanism 6 are disposed adjacent to a radially inward side of the inertia member 13 and the rivets 15.

As seen in FIG. 4, the second friction generation mechanism 6 has, in order in an axial direction from the flexible plate 11 toward the opposing portion 12 a of the second disk-like plate 12, friction washers 57, an input friction plate 58, and a cone spring 59. Thus, the flexible plate 11 has a function that accommodates the second friction generation mechanism 6 so that the number of components is reduced and the structure simplified.

The cone spring 59 imparts a load in the axial direction to friction surfaces. Further, the cone spring 59 is interposed and compressed between the opposing portion 12 a and the input friction plate 58, and therefore exerts an urging force on both members in the axial direction. Pawls 58 a formed on the radially outer edge of the input friction plate 58 are engaged with axially extending cutaway areas 12 b of the second disk-like plate 12. Thus, the input friction plate 58 is prevented from rotating relative to the second disk-like plate 12 by this engagement, but is movable in the axial direction.

As seen in FIG. 5, the friction washers 57 are composed of a plurality of members. The members are aligned and disposed in the direction of rotation, and each of these extends in the form of an arc. In this embodiment, there are preferably a total of six friction washers 57. Referring again to FIG. 4, the friction washers 57 are interposed between the input friction plate 58 and the annular portion 11 a of the flexible plate 11. In other words, the axial-direction engine side surface 57 a of the friction washers 57 makes contact in a slidable manner with the axial-direction transmission side surface of the flexible plate 11, and the axial-direction transmission side surface 57 b of the friction washers 57 makes contact in a slidable manner with the axial-direction engine side surface of the input friction plate 58. Referring now to FIGS. 4 and 6, concavities 63 are axially and rotationally formed in the inner circumferential surface of the friction washers 57. The concavities 63 are formed roughly in the center of the direction of rotation of the friction washers 57, and more specifically, have a bottom surface 63 a extending in the direction of rotation, and rotational direction end faces 63 b extending from both ends thereof in a roughly radial direction (roughly at a right angle from the bottom surface 63 a). In other words, the concavities open toward the axis of rotation O-O, with the bottom surface 63 a being arranged radially outward of its opening, and the rotational direction end faces 63 b extending radially inward from the bottom surface 63 a. The concavity 63 is formed in the axially middle portion of the inner circumferential surface of the friction washer 57 so that the concavity 63 has axial end faces 63 c and 63 d forming axial side surfaces.

A plurality of friction engagement members 60 is disposed to correspond to the concavities 63 of the friction washers 57. More specifically, the friction engagement members 60 are disposed radially inward of the friction washers 57 and within the concavities 63. The radially outer portion of the friction engagement member 60 is within the concavity 63. Both the friction washers 57 and friction engagement members 60 are preferably made of resin.

A friction engagement portion 64 including the friction engagement members 60 and the concavities 63 of the friction washer 57 is described below. The friction engagement members 60 have axial end faces 60 a and 60 b and rotational end faces 60 c. An outer circumferential surface 60 g of the friction engagement member 60 is adjacent to the bottom surface 63 a of the concavities 63. Further, a rotational direction gap 65 with a prescribed angle is defined between each of the rotational end faces 60 c and the rotational direction end faces 63 b. The total of both angles is a prescribed angle whose size allows the friction washer 57 thereof to rotate relative to the friction engagement members 60. This angle is preferably within a range that is equal to or slightly exceeds the damper operation angle created by small torsional vibrations caused by combustion fluctuations in the engine. In this embodiment, the friction engagement members 60 are disposed in the center of the direction of rotation of the concavities 63 in the neutral state shown in FIG. 6. Therefore, the size of the gap is the same on either side in the direction of rotation of the friction engagement members 60.

The friction engagement members 60 are engaged with the first plate 32 to rotate together with the first plate 32 and be movable in the axial direction. More specifically, an annular wall 32 a extending toward the engine in the axial direction is formed on the radially outer edge of the first plate 32, and concavities 61 indented on the internal side in the radial direction are formed corresponding to each friction engagement member 60 on the annular wall 32 a. In addition, a first slit 61 a penetrating in the radial direction at the rotational center of the concavity 61 and second slits 61 b penetrating in the radial direction are formed on both sides in the direction of rotation. The friction engagement members 60 have a first leg 60 e extending through the first slit 61 a radially inward. Furthermore, the friction engagement members 60 also have second legs 60 f that extend in both rotational directions which are in contact with the inner circumferential surface of the annular wall 32 a. The second legs 60 f extend through the second slits 61 b radially inward and extending outward in the direction of rotation. Moreover, the second legs 60 f make contact with the inner circumferential surface of the annular wall 32 a. As a result, the friction engagement members 60 do not move outwardly from the annular wall 32 a in the radial direction. In addition, the friction engagement members 60 have convexities 60 d that extend inward in the radial direction, and are engaged in the direction of rotation with the concavities 61 in the annular wall 32 a. The friction engagement members 60 are thereby integrally rotated as convexities of the first plate 32. In addition, the friction engagement member 60 can be attached to and detached from the first plate 32 in the axial direction.

The friction engagement member 60 can move relative to the friction washer 57 because the axial and rotational lengths of the friction engagement member 60 are shorter than the axial and rotational lengths of the concavity 63. In other words, the distance between the axial end faces 63 c and 63 d is longer than the axial length of the axial end faces 60 a and 60 b of the friction engagement member 60, as is the rotational length between the rotational direction end faces 63 b of the concavity 63 and the end faces 60 c of the engagement member 60. Further, the friction engagement member 60 can also tilt relative to the friction washer 57 to a certain angle because a radial space is also provided between the outer circumferential surface 60 g of the friction engagement member 60 and the bottom surface 63 a of the concavity 63.

As described above, the friction washer 57 is frictionally engaged with the flexible plate 11 and the input friction plate 58 in a manner that allows movement in the direction of rotation, and is engaged in a manner that allows torque to be transmitted to the friction engagement members 60 by way of the rotational direction gap 65 in the engagement portion 64. The friction engagement members 60 can also integrally rotate with the first plate 32, and move relatively in the axial direction.

Next, referring to FIGS. 4-6, the relationship between the friction washer 57 and the friction engagement members 60 is described in greater detail. The widths in the direction of rotation (the angles in the direction of rotation) of the friction engagement members 60 are all the same, but some of the widths in the direction of rotation (the angles in the direction of rotation) of the concavities 63 are different. That is to say, there are at least two types of friction washers 57 having concavities 63 with differing widths in the rotation direction. In this embodiment, the friction washers 57 are made of first and second friction washers 57A and 57B. Two first friction washers 57A face each other in the up and down directions in FIG. 5, and four second friction washers 57B that face each other in the left and right directions. The first friction washers 57A and concavities 63, and the second friction washers 57B and concavities 63 respectively form first and second engagement portions 64A and 64B. The first friction washers 57A and the second friction washers 57B have roughly the same shape, and are made of the same material. The only major point in which the first and second friction washers 57A and 57B differ is the length in the direction of rotation (the angles in the direction of rotation) of the rotational direction gap of the concavities 63. More specifically, the length in the direction of rotation of the concavities 63 of the second friction washers 57B is larger than the length in the direction of rotation of the concavities 63 of the first friction washers 57A. As a result, concavities 63 of the first friction washers 57A and the friction engagement members 60 have first rotational direction gaps 65A, while concavities 63 of the second friction washers 57B and the friction engagement members 60 have second rotational direction gaps 65B. Further, the second rotational direction gap 65B of the second engagement portion 64B in the second friction washers 57B is larger than the first rotational direction gap 65A of the first engagement portion 64A in the first friction washers 57A. In this embodiment, the former is preferably 10° and the latter is preferably 8°, for a difference of 2°, for example.

The first and second friction washers 57A and 57B are disposed and aligned in the direction of rotation, and both edges thereof in the direction of rotation are adjacent to each other. The first and second friction washers 57A and 57B are arranged to alternate between one first friction washer 57A for every two second friction washers 57B in the rotation direction. The angle between the edges of the washers 57A and 57B in the direction of rotation is set to a value that is greater than the difference (2°, for example) between the second rotational direction gap 65B in the second friction washers 57B and the first rotational direction gap 65A in first friction washers 57A.

6) Clutch Disk Assembly

Referring now to FIGS. 1 and 2, the clutch disk assembly 93 has a friction facing 93 a disposed axially between the first friction surface 3 a of the second flywheel 3 and a pressure plate 98. Further, the clutch disk assembly has a hub 93 b spline-engaged with the transmission input shaft 92.

7) Clutch Cover Assembly

The clutch cover assembly 94 is primarily formed of a clutch cover 96, a diaphragm spring 97, and the pressure plate 98. The clutch cover 96 is an annular disk-like member fixed to the second flywheel 3. The pressure plate 98 is an annular member having a pressing surface adjacent to the friction facing 93 a and rotates together with the clutch cover 96. The diaphragm spring 97 is supported by the clutch cover 96 to urge elastically the pressure plate 98 toward the second flywheel 3. When a release device not shown pushes the radially inner end of the diaphragm spring 97 toward the engine, the diaphragm spring 97 releases the load axially placed on the pressure plate 98.

(2) Operation

1) Torque Transmission

Referring to FIGS. 1-3, in this double mass flywheel 1, a torque supplied from the crankshaft 91 of the engine is transmitted to the second flywheel 3 via the damper mechanism 4. In the damper mechanism 4, the torque is transmitted through the input disk-like plate 20, coil springs 34-36, and output disk-like plates 32 and 33 in this order. Further, the torque is transmitted from the double mass flywheel 1 to the clutch disk assembly 93 in the clutch engaged state and is finally provided to the input shaft 92.

2) Absorption and Attenuation of Torsional Vibrations

When the double mass flywheel 1 receives combustion variations from the engine, the damper mechanism 4 operates to rotate the input disk-like plate 20 relatively to the output disk-like plates 32 and 33 so that the coil springs 34-36 are compressed in parallel in the rotational direction. Further, the first friction generation mechanism 5 and the second friction generation mechanism 6 generate a predetermined hysteresis torque. Through the foregoing operations, the torsional vibrations are absorbed and damped.

Next, the operation of the damper mechanism 4 is described referring to FIG. 15 and to the torsional characteristics of FIG. 16. In a small torsional angle area around zero degrees, only the first coil springs 34 are compressed to achieve a relatively low rigidity. As the torsional angle becomes larger, the first coil springs 34 and the second coil spring 35 are compressed in parallel to achieve a relatively high rigidity. As the torsional angle becomes even larger, the first coil springs 34, the second coil springs 35, and the third coil springs 36 are compressed in parallel to achieve the highest rigidity allowed at the ends of the torsional characteristics. The first friction generation mechanism 5 operates over the entire torsional angle range. The second friction generation mechanism 6 does not operate within certain angles on either side of the torsional angle after the direction of the torsional action changes.

Next, referring to FIGS. 4-6 and 15, the operation performed when the friction washer 57 is driven by the friction engagement member 60 is described. The operation in which the friction engagement member 60 is twisted from the neutral state in the rotation direction RI in relation to the friction washer 57 is described.

When the torsion angle increases, the first friction engagement member 60 in the first friction washers 57A eventually make contact with the rotational direction end face 63 b on the rotational direction R1 side of the concavities 63 of the first friction washers 57A. At this time, the friction engagement member 60 in the second friction washers 57B have a rotational direction gap (which is half the difference between the second rotation direction gap 65B of the second friction washers 57B and the first rotational direction gap 65A of the first friction washers 57A, and is 1° in this embodiment) in the rotational direction end face 63 b of the concavities 63 of the second friction washers 57B in the rotational direction R1.

When the torsion angle further increases, the friction engagement member 60 drives the first friction washers 57A, and causes them to slide in relation to the flexible plate 11 and the input friction plate 58. At this time, the first friction washers 57A approach the second friction washers 57B in the rotational direction R1, but the edge portions of both of these do not make contact.

When the torsion angle finally achieves a prescribed magnitude, the friction engagement members 60 make contact with the rotational direction end face 63 b of the concavities 63 of the second friction washers 57B. After this, the friction engagement members 60 drives both the first and second friction washers 57A and 57B, causing them to slide in relation to the flexible plate 11 and the input friction plate 58.

In summation, driving the friction washer 57 with the aid of the first plate 32 yields an area in which some number of plates is driven to generate an intermediate frictional resistance in the torsion characteristics before the start of the large frictional resistance area in which all of the plates are driven.

2-1) Small Torsional Vibrations

The operation of the damper mechanism 4 when small torsional vibrations caused by combustion fluctuations of the engine are input to the double mass flywheel 1 is described below with reference to the mechanical circuit diagram in FIG. 15 and the diagrams of torsional characteristics in FIGS. 16 to 19.

When small or minute torsional vibrations are input, the input disk-like plate 20 in the second friction generation mechanism 6 rotates relative to the friction washers 57A and 57B in the rotational direction gaps 65A and 65B between the friction engagement member 60 and the concavities 63. In other words, the friction washer 57 is not driven with the input disk-like plate 32, and the friction washers 57A and 57B therefore do not rotate in relation to the member on the input side. As a result, high hysteresis torque is not generated for small torsional vibrations. That is, although the coil springs 34 and 36 operate at “AC 2HYS,” for example, in the diagram of torsional characteristics in FIG. 16, slippage does not occur in the second friction generation mechanism 6. That is to say, only a hysteresis torque that is much smaller than a normal hysteresis torque can be obtained in a prescribed range of torsion angles. Thus, the vibration and noise level can be considerably reduced because a very narrow rotational direction gap is provided in which the second friction generation mechanism 6 does not operate in the prescribed angle range.

As a result, when the operating angle of the torsional vibration is equal to or less than the angle (8°, for example) of the first rotational direction gap 65A of the first engagement portion 64A of the first friction washers 57A, large frictional resistance (high hysteresis torque) is not generated at all, and only area A of low frictional resistance is obtained in the second stage of torsion characteristics, as shown in FIG. 17. Moreover, when the operating angle of the torsional vibration is equal to or greater than the angle (8°, for example) of the first rotational direction gap 65A of the first engagement portion 64A of the first friction washers 57A, and is equal to or less than the angle (10°, for example) of the second rotational direction gap 65B of the second engagement portion 64B of the second friction washers 57B, the area B of intermediate frictional resistance is generated on the edge of the area A of low frictional resistance, as shown in FIG. 18. When the operating angle of the torsional vibration is equal to or greater than the angle (10°, for example) of the second rotational direction gap 65B of the second engagement portion 64B of the second friction washers 57B, the area B of intermediate frictional resistance and the area C in which some large frictional resistance is generated are respectively obtained on both edges of the area A of low frictional resistance, as shown in FIG. 19.

2-2) Wide-Angle Torsional Vibrations

Operation of the second friction generation mechanism 6 when wide-angle torsional vibrations are input will be explained. In the second friction generation mechanism 6, the friction washers 57A and 57B rotate together with the friction engagement members 60 and the first plate 32, and relative to the flexible plate 11 and the friction plate 58. As a result, the friction washers 57A and 57B and the friction engagement member 60 slide against the flexible plate 11 and the input friction plate 58 to generate frictional resistance.

As described above, when the torsional angle of the torsional vibration is large, the friction washers 57A and 57B rotate together with the friction engagement members 60 and the first plate 32 and slide against the flexible plate 11 and the input friction plate 58. As a result, the friction washers 57A and 57B slide against the flexible plate 11 and the input friction plate 58 to generate a frictional resistance over the entire range of torsional characteristics.

Here, the operation in the edge portion (position in which the direction of the vibration changes) of the torsion angle is described. At the right-hand edge of the torsion characteristic line chart of FIG. 16, the friction washers 57A and 57B are shifted most in the rotational direction R2 in relation to friction engagement member 60. When the friction engagement member 60 twists from this state in the rotational direction R2 in relation to the output disk-like plates 32 and 33, the friction washers 57A and 57B and the friction engagement member 60 rotate relative to each other across the entire angle of the rotational direction gaps 65A and 65B of the friction engagement member 60 and concavities 63. During this operation, the area A (8°, for example) of low frictional resistance can be obtained because the friction washers 57A and 57B do not slide against the member on the input side. Next, when the first rotational direction gap 65A of the first engagement portion 64A of the first friction washers 57A is no longer present, the first plate 32 drives the first friction washers 57A. Then, the first friction washers 57A rotate relative to the flexible plate 11 and the input friction plate 58. As a result, the area B of intermediate frictional resistance (2°, for instance) is generated as described above. When the second rotational direction gap 65B of the second engagement portion 64B of the second friction washers 57B is no longer present, the first plate 32 subsequently drives the second friction washers 57B. Then, the second friction washers 57B rotate relative to the flexible plate 11 and the input friction plate 58. The area C of comparatively large frictional resistance is generated because both the first friction washers 57A and the second friction washers 57B slide at this time. In addition, hysteresis torque generated by the friction washers 57A is lower than that generated by the second friction washers 57B and preferably the former is almost half of the latter in this embodiment.

As described above, the area B of intermediate frictional resistance is provided at an early stage of a large frictional resistance generation. A barrier of high hysteresis torque does not exist when a large frictional resistance is generated because the buildup of large frictional resistance is graduated in this manner. As a result, the knocking sound of the pawls when high hysteresis torque is generated decreases in a frictional resistance generation mechanism with a very narrow rotational direction gap to absorb small torsional vibrations.

In particular, the number of types of frictional members can be kept low in the present invention because a single type of friction washer 57 is used to generate intermediate frictional resistance. The friction washer 57 is also a simple structure that extends in the form of an arc. Furthermore, a through-hole in the axial direction is not formed in the friction washer 57, and thus, manufacturing costs can be kept low.

(3) Advantages

3-1) First Friction Generation Mechanism

The sliding area of the first friction generation mechanism 5 is set to be relatively large because the first friction generation mechanism 5 makes use of a part of the second flywheel 3 as a friction surface. Specifically, as shown in FIGS. 7 and 8, the second friction member 52 is urged against the second flywheel 3 by the cone spring 53. Accordingly, the pressure per area on the sliding surface is reduced so that the life of the first friction generation mechanism 5 is prolonged.

The radially outer portion of the second friction member 52 and the radially inward portion of the first and second coil springs 34 and 35 overlap in the axial direction. That is to say, the radial position of the outer circumferential edge of the second friction member 52 is radially outward of a radial position of the inner circumferential edge of the first and second coil springs 34 and 35. Accordingly, although the second friction member 52 and the first and second coil springs 34 and 35 are very close to each other in the radial direction, it is possible to provide an adequate or superior friction area in the second friction generation mechanism 6,

The radially outer portion of the annular portion 51 a of the first friction member 51 and radially inner portions of the first and second coil springs 34 and 35 overlap when view along the axis of rotation. Further, a radial position of radially outer edges of the annular portion 51 a is radially outward that of radially inner edges of the first and second coil springs 34 and 35. It is possible to provide a large friction surface for the first frictional resistance mechanism 5 even though the annular portion 51 a and the first and second coil springs 34 and 35 are very closely located in the radial direction.

Only the first friction member 51 is nonrotatably engaged with the input disk-like plate 20 and the first friction member 51 and the second friction member 52 are nonrotatably engaged with each other. Accordingly, it is unnecessary to engage directly the second friction member 52 with the input disk-like plate 20, thereby making the structure simpler.

As shown in FIGS. 7, 8, and 10, the first friction member 51 is composed of the annular portion 51 a in contact with the first plate 32 to slide in the rotational direction, and a plurality of the engagement portions 51 b and 51 c extending from the annular portion 51 a and engaging with the input disk-like plate 20 to move relatively in the axial direction but not in the rotational direction. The second friction members 52 are formed with a plurality of recesses 52 a with which the engagement portions 51 b and 51 c are engaged to move in the axial direction but not in the rotational direction. Accordingly, it is easy to realize a structure in which the annular portion 51 a of the first friction member 51 and the second friction member 52 are disposed apart from each other in the axial direction because the first friction member 51 has the engagement portions 51 b and 51 c extending axially.

The cone spring 53 is disposed between the second friction member 52 and the engagement portions 51 b and 51 c of the first friction member 51 and urges both the members in the axial direction, thereby making the structure simpler.

The washer 54 is seated on the tip of the engagement portions 51 b and 51 c of the first friction member 51 and receives a load from the cone spring 53. The washer 54 provides the axial load applied to the friction sliding surface so that the frictional resistance generated on the sliding surface is stable.

As seen in FIG. 1, the first friction generation mechanism 5 is disposed radially inward of the clutch friction surface 3 a of the second flywheel 3, and apart from each other. Accordingly, the first friction generation mechanism 5 is unlikely to be affected by the heat from the clutch friction surface 3 a, thereby stabilizing frictional resistance.

The first friction generation mechanism 5 is disposed radially inward of the radial center of the first and second coil springs 35 and radially outward of the radially outermost edge of the bolts 22, thereby ensuring a structure with a small space.

3-2) Second Friction Generation Mechanism 6

As seen in FIGS. 1, 2, and 4, the second friction generation mechanism 6 is unlikely to be affected by the heat from the clutch friction surface 3 a of the second flywheel 3 and has stable characteristics because the second friction generation mechanism 6 is held by the first flywheel 2, more specifically by the flexible plate 11. In particular, the first flywheel 2 is unlikely to receive the heat from the second flywheel 3 because the first flywheel 2 is connected to the second flywheel 3 by way of the coil springs 34-36. Further, the clutch friction surface 3 a is on a side of the second flywheel 3 that is axially opposite the second friction generation mechanism 6.

The second friction generation mechanism 6 makes use of the annular portion 11 a of the flexible plate 11 as a friction surface so that the number of components of the second friction generation mechanism 6 is reduced and the structure simplified.

The second friction generation mechanism 6 is disposed radially outward of the clutch friction surface 3 a and apart from each other in the radial direction so that the second friction generation mechanism 6 is unlikely to be affected by the heat from the clutch friction surface 3 a.

3-3) Flexible Flywheel (First Flywheel 2 and Damper Mechanism 4)

The first flywheel 2 is composed of the inertia member 13 and the flexible plate 11 to connect the inertia member 13 to the crankshaft 91 and is elastically deformable in the bending direction, which is substantially parallel to the axis of rotation of the crankshaft 91. The damper mechanism 4 is composed of the input disk-like plate 20 to which the torque is inputted from the crankshaft 91, the output disk-like plates 32 and 33 disposed rotatable relative to the input disk-like plate 20, and the coil springs 34-36 arranged to be compressed in the rotational direction by the relative rotation of both the members. The first flywheel 2 can move in the bending direction within limits relative to the damper mechanism 4. A combination of the first flywheel 2 and the damper mechanism 4 constitute a flexible flywheel.

When bending vibrations are inputted to the first flywheel 2, the flexible plate 11 deforms in the bending direction to absorb the bending vibrations from the engine. In this flexible flywheel, the bending vibration absorption effect by the flexible plate 11 is very high because the first flywheel 2 can move in the bending direction relative to the damper mechanism 4.

The flexible flywheel further includes the second friction generation mechanism 6. The second friction generation mechanism 6 is disposed between the first flywheel 2 and output disk-like plate 32 of the damper mechanism 4 and operates in parallel with the coil springs 34-36 in the rotational direction. The second friction generation mechanism 6 has the friction washers 57A and 57B and the friction engagement members 60, which are engaged with each other not only to transmit the torque but also to move in the bending direction relative to each other. In this flexible flywheel, the first flywheel 2 can move relative to the damper mechanism 4 in the bending direction within limits even though they are engaged with each other by way of the second friction generation mechanism 6 because two members are engaged with each other to move relatively in the bending direction. As a result, the bending vibration absorption effect by the flexible plate 11 is very high.

The friction washers 57A and 57B and the friction engagement member 60 are engaged with each other with the rotational direction gaps 65A and 65B in the rotational direction. Large resistance is not generated by the relative movement in the bending direction because they are not in close contact with each other in the rotational direction.

The friction engagement member 60 is engaged with the output disk-like plates 32 and 33 to move in the axial direction. Therefore, axial resistance is unlikely to be generated between the friction engagement member 60 and the output disk-like plates 32 and 33 in the axial direction when the friction washer 57 moves together with the first flywheel 2 in the axial direction.

3-4) Third Coil Spring 36

Referring now to FIGS. 1 and 3, the third coil springs 36 starts operation in the area where torsional angle becomes large to apply adequate stopper torque to the damper mechanism 4. The third coil springs 36 are functionally disposed in parallel to the first and second coil springs 34 and 35 in the rotational direction.

The third coil spring 36 respectively has a wire diameter and coil diameter smaller by approximately half than those of the first and second coil springs 34 and 35, thereby making the occupied axial space smaller when compared to conventional structures. As shown in FIGS. 1 and 3, the third coil springs 36 are disposed radially outward of the first and second coil springs 34 and 35 and correspond to the clutch friction surface 3 a of the second flywheel 3 in the radial direction. In other words, radial position of the third coil springs 36 is within an annular area defined by the inner circumferential edge and the outer circumferential edge of the clutch friction surface 3 a.

In this embodiment, providing the third coil springs 36 improves the capability of the flywheel assembly by raising the stopper torque. Further, only a small amount space is used for the third coil springs 36 because of the dimension and location of the third coil springs 36. Moreover, the coil diameter of each third coil spring 36 is smaller than those of the first and second coil springs 34 and 35 so that the axial length of the whole area where the third coil spring 36 is disposed is relatively small. Preferably, the coil diameter of the third coil spring 36 is in the range of 0.3-0.7 of the coil diameter of the first and second coil springs 34 and 35. As a result, although the third coil springs 36 are disposed at a place corresponding to the clutch friction surface 3 a of the second flywheel, where the axial thickness is the largest in the second flywheel 3, the axial length of the area where third coil spring 36 is disposed is relatively small, and, in fact, is smaller than the area where the first and second coil springs 34 and 35 are disposed.

In addition, the radial position of the stopper mechanism 71 composed of the projections 20 c of the input disk-like plate 20 and the contact portions 43 and 44 of the output disk-like plates 32 and 33 is within the annular area of the clutch friction surface 3 a, and is disposed at the same radial position with the third coil springs 36. Therefore, the radial dimension of the whole structure is smaller relative to structures in which the members are located at different radial positions.

Alternate Embodiments

Alternate embodiments will now be explained. In view of the similarity between the first and alternate embodiments, the parts of the alternate embodiments that are identical to the parts of the first embodiment will be given the same reference numerals as the parts of the first embodiment. Moreover, the descriptions of the parts of the alternate embodiments that are identical to the parts of the first embodiment may be omitted for the sake of brevity.

2. Second Embodiment

Next, a structure of a second friction generation mechanism 107 according to a second embodiment of the present invention will be explained initially referring to FIG. 20. Explanation regarding parts and structure that are the same as those of the first embodiment will be omitted and differences will be highlighted.

As shown in FIG. 20, the second friction generation mechanism 107 operates between an input disk-like plate and output disk-like plates 132 and 133 of the damper mechanism in parallel with the coil springs in the rotational direction. The second friction generation mechanism 107 generates a relatively large frictional resistance (hysteresis torque) over the whole range of the torsional characteristics when the second flywheel 103 rotates relative to the crankshaft.

As shown in FIG. 20, the second friction generation mechanism 107 is made of a plurality of members contacting each other and disposed in an axial space between an annular portion 111 a at the radially outer portion of a flexible plate 111 and an inertia member 113. More specifically, the inertia member 113 has an annular protrusion 113 a facing the annular portion 111 a arranged to have a distance between it and the flexible plate 111 and the inertia member 113 in the axial direction. The inertia member 113 is formed with an inner circumferential surface 113 c on the engine side of the annular protrusion 113 a in the axial direction.

As seen in FIG. 20, the second friction generation mechanism 107 has, in order in an axial direction from the flexible plate 111 toward an axial-direction engine side surface 113 b of the inertia member 113, a cone spring 158, a friction plate 159, and friction washers 161. Thus, the flexible plate 111 has a function that accommodates the second friction generation mechanism 107 so the number of components is reduced and the structure simplified. Moreover, the inertia member 113 has the same function.

The cone spring 158 imparts a load in the axial direction to friction surfaces of the other members. Furthermore, the cone spring 158 is interposed and compressed between the annular portion 111 a and the friction plate 159, and therefore exerts an urging force on both members in the axial direction.

Pawls 159 a formed on the radially inner edge of the friction plate 159 are bent and extend in the axial direction to engage with cutaway areas 111 b of the annular portion 111 a of the flexible plate 111. Thus, the friction plate 159 is prevented from rotating relative to the flexible plate 111 by this engagement, but is movable in the axial direction.

The friction washers 161 are composed of a plurality of members as explained in the first embodiment. The members are aligned and disposed in the direction of rotation, and each of these extends in the form of an arc. In this embodiment, there are preferably a total of six friction washers 161. The friction washers 161 are interposed between the friction plate 159 and the inertia member 113. In other words, the axial-direction engine side surface 161 a of the friction washers 161 makes contact in a slidable manner with the axial-direction transmission side surface 111 c of the flexible plate 111, and the axial-direction transmission side surface 161 b of the friction washers 161 makes contact in a slidable manner with the axial-direction engine side surface 113 b of the inertia member 113. The outer circumferential surface 161 c of the friction washers 161 is in contact with the inner circumferential surface 113 c of the inertia member 113.

In summary, the second friction generation mechanism 107 is disposed within a space between the axial-direction engine side surface 113 b of the inertia member 113 and the axial-direction transmission side surface 111 c of the flexible plate 111. The second friction generation mechanism 107 has friction washers 161 contacting the axial-direction engine side surface 113 b of the inertia member 113, the friction plate 159 engaged with the flexible plate 111 to move in the axial direction but not to rotate relatively, the cone spring 158 disposed between the axial-direction transmission side surface 111 c of the flexible plate 111 and the friction plate 159 to urge elastically the friction plate 159 toward the friction washers 161.

As mentioned above, the second friction generation mechanism 107 utilizes a part of the inertia member 113 as a friction surface. In other words, the inertia member 113 is an integral member replacing the inertia member 13 and the second disk-like member 12 in the first embodiment. As a result, the second friction generation mechanism 107 has relative few components and an overall simple structure, thereby lowering the cost. Furthermore, the heat of the second friction generation mechanism 107 is absorbed by the inertia member 113 so that the second friction generation mechanism 107 realizes a stable hysteresis torque and less wear because the inertia member 113 has a large thickness in the axial direction and has a large heat capacity. Moreover, the omission of the second disk-like plate 12 makes it easy to enlarge the inertia member 113.

Unlike the first embodiment, the friction washers 161 are not in contact with the flexible plate 111 so that abnormal sound is unlikely to diffuse into the flexible plate 111 when the second friction generation mechanism 107 operates.

Referring to FIG. 21, a modification of the second embodiment will be explained. The friction plate 159 is formed with a plurality of the claws 159 b at the radially outer edge. The claws 159 b extend radially outward and are engaged with cutaways 111 d of the radially outermost portion of the flexible plate 111 contacting the inertia member 113. By this engagement, the friction plate 159 is engaged with the flexible plate 111 to move in the axial direction but not to rotate relatively.

3. Other Embodiments

Embodiments of the double mass flywheel in accordance with the present invention were described above, but the present invention is not limited to those embodiments. Other variations or modifications that do not depart from the scope of the present invention are possible. More particularly, the present invention is not limited by the specific numerical values of angles and the like described above.

In the above-described embodiment, two size types of the rotational direction gap of the engagement portion were used, but it is also possible to use three or more size types. In the case of three size types, the magnitude of the intermediate frictional resistance will have two stages (the case of the third embodiment described hereinafter).

The coefficients of friction of the first friction member and the second friction member are the same in the above-described embodiment, but these may also be varied. Thus, the ratio of the intermediate frictional resistance and large frictional resistance can be set by adjusting the frictional resistance generated by the first friction member and the second friction member according to operating needs.

In the above-described embodiment, the intermediate frictional resistance is generated by providing the friction engagement member with an equal size and concavities with different sizes, but the concavities may be set to an equal size and the size of the friction engagement member may be different. Furthermore, combinations of the friction engagement members and concavities with different sizes may also be used.

In the above-described embodiment, the concavity of the friction washer faces the internal side in the radial direction, but it may face the external side in the radial direction.

In addition, the friction washer in the above-described embodiment has concavities, but the friction washer may also have convexities. In this case, the input side disk-like plate has concavities, for example.

Furthermore, the friction washer in the above-described embodiment has a friction surface that is frictionally engaged with an input member, but it may also have a friction surface that is frictionally engaged with an output member. In this case, an engagement portion having a rotational direction gap is formed between the friction washer and an input side member.

As used herein, the following directional terms “forward, rearward, above, downward, vertical, horizontal, below, and transverse” as well as any other similar directional terms refer to those directions of a device equipped with the present invention. Accordingly, these terms, as utilized to describe the present invention should be interpreted relative to a device equipped with the present invention.

The term “configured” as used herein to describe a component, section or part of a device includes hardware and/or software that is constructed and/or programmed to carry out the desired function.

Moreover, terms that are expressed as “means-plus function” in the claims should include any structure that can be utilized to carry out the function of that part of the present invention.

The terms of degree such as “substantially,” “about,” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. For example, these terms can be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies.

This application claims priority to Japanese Patent Applications No. 2003-323630 and No. 2004-141342. The entire disclosure of Japanese Patent Applications No. 2003-323630 and No. 2004-141342 is hereby incorporated herein by reference.

While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. Furthermore, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. Thus, the scope of the invention is not limited to the disclosed embodiments. 

1. A double mass flywheel configured to receive torque from a crankshaft of an engine, comprising: a first flywheel being fixed to the crankshaft; a second flywheel being formed with a clutch friction surface; an elastic member being configured to connect elastically and directly said second flywheel to the crankshaft in a rotational direction; and a friction generation mechanism being arranged to operate functionally in parallel with said elastic member in said rotational direction, said friction generation mechanism being held by said first flywheel.
 2. The double mass flywheel according to claim 1, wherein said first flywheel includes a plate member that has a radially inner end fixed to the crankshaft, and an inertia member fixed to a radially outer end of said plate member.
 3. The double mass flywheel according to claim 2, wherein said friction generation mechanism is held by a radially outer portion of said plate member.
 4. The double mass flywheel according to claim 3, wherein said first flywheel further includes a second plate member fixed to a radially outer portion of said plate member to define an axial space with said plate member, and said friction generation mechanism is disposed within said space.
 5. The double mass flywheel according to claim 3, wherein said friction generation mechanism utilizes a part of said inertia member as a friction surface.
 6. The double mass flywheel according to claim 5, wherein said friction generation mechanism is located within a space between an axially engine-side surface of said inertia member and an axially transmission-side surface of said plate member, and said friction generation mechanism includes a friction member that contacts said axially engine-side surface of said inertia member, a plate nonrotatably and axially movably engaged with said plate member, and an urging member located between said axially transmission-side surface of said plate member and said plate to urge elastically said plate toward said friction member.
 7. The double mass flywheel according to claim 6, wherein said plate member is a flexible plate deformable in a bending direction parallel to an axis of rotation of the crankshaft.
 8. The double mass flywheel according to claim 7, wherein said friction generation mechanism is located radially outward of said clutch friction surface.
 9. The double mass flywheel according to claim 2, wherein said friction generation mechanism utilizes a part of said inertia member as a friction surface.
 10. The double mass flywheel according to claim 9, wherein said friction generation mechanism is located within a space between an axially engine-side surface of said inertia member and an axially transmission-side surface of said plate member, and said friction generation mechanism includes a friction member that contacts said axially engine-side surface of said inertia member, a plate nonrotatably and axially movably engaged with said plate member, and an urging member located between said axially transmission-side surface of said plate member and said plate to urge elastically said plate toward said friction member.
 11. The double mass flywheel according to claim 2, wherein said plate member is a flexible plate deformable in a bending direction parallel to an axis of rotation of the crankshaft.
 12. The double mass flywheel according to claim 1, wherein said friction generation mechanism is located radially outward of said clutch friction surface.
 13. The double mass flywheel configured to receive torque from a crankshaft of an engine, comprising: an inertia member; a flexible plate being deformable in a bending direction parallel to an axis of rotation of the crankshaft, said flexible plate connecting said inertia member to the crankshaft; a second flywheel being formed with a clutch friction surface; an elastic member being configured to connect elastically said second flywheel to the crankshaft in a rotational direction; and a friction generation mechanism being arranged to operate functionally in parallel with said elastic member in said rotational direction, said friction generation mechanism being held by said flexible plate.
 14. The double mass flywheel according to claim 13, wherein said friction generation mechanism utilizes a part of said flexible plate as a friction surface.
 15. The double mass flywheel according to claim 9, wherein said friction generation mechanism utilizes a part of said inertia member as a friction surface.
 16. The double mass flywheel according to claim 15, wherein said frictional resistance mechanism is located within a space between an axially engine-side surface of said inertia member and an axially transmission-side surface of said flexible plate, and said friction generation mechanism includes a friction member contacting said axially engine-side surface of said inertia member, a plate nonrotatably and axially movably engaged with said flexible plate, and an urging member located between said axially transmission-side surface of said flexible plate and said plate to urge elastically said plate toward said friction member.
 17. The double mass flywheel according to claim 16, wherein said friction generation mechanism is located radially outward of said clutch friction surface.
 18. The double mass flywheel according to claim 17, further comprising a fixing member to fix said inertia member to said flexible plate, said friction generation mechanism is located adjacent to a radially inner side of said fixing member.
 19. The double mass flywheel according to claim 13, wherein said friction generation mechanism is located radially outward of said clutch friction surface.
 20. The double mass flywheel according to claim 13, further comprising a fixing member to fix said inertia member to said flexible plate, said friction generation mechanism is located adjacent to a radially inner side of said fixing member. 